Process for the separation of long chain amino acids and dibasic acids

ABSTRACT

There is disclosed a process for the separation of long chain amino acid and long chain dibasic acid, comprising: (1) recovering alkylamine from an aqueous solution of an alkali hydroxide hydrolysis of the mixed amide derivatives by distilling or by extracting with an extractant solvent; (2) cooling the aqueous solution of step (1) to precipitate a mixed alkali salts of long chain amino acid and dibasic acid; (3) recovering the mixed alkali salts of long chain amino acid and dibasic acid to provide a mother liquor; (4) separating long chain amino acid and dibasic acid by acidification-extraction of long chain dibasic acid with an extractant solvent or by selective dissolution of alkali salt of long chain amino acid in an aqueous solvent; and (4) adding an acid to the mother liquor of step (3) to obtain alkanoic acid.

CROSS REFERENCE

This application is a continuation-in-part of the co-pending applicationSer. No. 15/635,874, filed on Jun. 28, 2017, which is incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates to a process for the separation of longchain amino acids, long chain dibasic acids, short chain alkylamines,and short chain alkanoic acids.

BACKGROUNDS OF THE INVENTION

Long chain saturated aliphatic amino acids, lactams, and dibasic acidsare important monomers for long chain nylons and engineering plastics.Nylons are a class of polymers that contain amide bond on their backboneof chains. Nylons are one of the most widely used, most numerous intypes, and most consumed class of engineering plastics.

Because of their unusual molecular structure, long chain nylons possessextraordinary physical properties, i.e., higher mechanical strength thanmetal, low hygroscopicity, excellent resistance to oil, low temperature,abrasion, and chemical corrosion, and most importantly, easy tofabricate. Long chain nylons are made into many kinds of plasticsproducts, spun to fibers, and stretched to thin films. Long chain nylonsare also used in paints and hot melt adhesives. Hence, long chain nylonsfind wide applications in automobile, electrical, electronic,telecommunications, petrochemical, and aerospace industries.

Long chain amino acids and lactams are used industrially as monomers toproduce nylon-9, nylon-11, and nylon-12.

Long chain dibasic acids are condensed with diamines industrially asstarting materials to produce nylon-610, nylon-612, nylon-510,nylon-512, nylon-1010, and nylon-1212.

WO 2017/088218 and the co-pending U.S. Ser. No. 15/601,556 both by thepresent inventor, both of which are incorporated by reference herein,disclose a novel process for the coproduction of long chain amino acidsand dibasic acids from keto fatty acid derivatives. According to thedisclosed process, long chain keto fatty acid derivatives are reactedwith hydroxylamine to form an oxime derivative, which is subjected tothe Beckmann rearrangement to yield a mixture of two amide derivatives.These amide derivatives are hydrolyzed to a mixture of productscontaining long chain amino acids and dibasic acids, which are isolatedby a process of step-wise neutralization in a highly diluteconcentration. Thus, a substantial amount of energy is required for theconcentration, so that the process is not economical.

Moreover, the present inventor has found that long chain amino acids anddibasic acids of required quality for the production of polyamidescannot be obtained, if the process according these prior disclosures isapplied for commercial starting materials, which contain various amountof other fatty acids. Apparently, these impurities contaminate intendedproducts and thus demand a process for their removal from final productsof required purity.

Hydrolysis of the mixed amide derivatives from the Beckmannrearrangement yields not only long chain amino acids and dibasic acids,but also short chain alkyl amines and alkanoic acids. There is a lack ofany method for the separation and recovery of these short chain productsfrom the mixture of the hydrolysis reaction.

It is desirable to have a process for the separation of each componentto their required purity from their complex mixture to achieve aneconomical process and to reduce or eliminate the disposal of wastestream.

It is an object of the present invention to disclose a process for theseparation of long chain amino acids, dibasic acids, short chain alkylamines, short chain alkanoic acids, and for the recovery of other fattyacids present in the commercial starting materials, such as stearicacid, and impurities generated as byproducts of the productionreactions. By the process of the present invention, long chain aminoacids and dibasic acids are separated simply, efficiently, andeconomically with high yields and excellent purity.

It is another object of the present invention to disclose a process forthe recovery of long chain amino acids and inorganic salts from aqueouswaste mother liquor. As a result, there is no aqueous waste dischargefrom production process.

DESCRIPTION OF THE DRAWINGS

FIG. 1. Schematic flowchart for the separation of long chain amino acid,dibasic acid, alkylamine, and alkanoic acid from their mixture in thecase of an alkali hydroxide hydrolysis.

FIG. 2. Schematic flowchart for the separation of long chain amino acid,dibasic acid, alkylamine, and alkanoic acid from their mixture in thecase of an acid hydrolysis.

FIG. 3. Schematic flowchart for the recovery of long chain amino acidand alkali salt from waste aqueous stream with the aid of an alkalihydroxide.

FIG. 4. Schematic flowchart for the recovery of long chain amino acidand alkali salt from waste aqueous stream with the aid of an acid.

FIG. 5. Schematic flowchart for the treatment of aqueous stream torecover alkylamine, long chain amino acid, and alkali salt for an acidhydrolysis of mixed amide derivatives.

FIG. 6. Solubility curve of 11-aminoundecanoic acid in water at neutralpH, 1 M solution of sulfuric acid, and 2 M solution of sodium hydroxide.

FIG. 7. Solubility curve of heptanoic acid in a 6 M solution of sodiumhydroxide and dodecanedioic acid in a 3 M solution of sodium hydroxide.

FIG. 8. Solubility of 11-aminoundecanoic acid and dodecanedioic acid inaqueous ethanol solution of 2 M sodium hydroxide at differentconcentration of ethanol.

FIG. 9. Schematic flowchart for the separation of alkali salts for longchain amino acid and dibasic acid from a mixture of an alkali hydroxidehydrolysis.

FIG. 10. Schematic flowchart for the separation of alkali salt of longchain amino acid and long chain dibasic acid from their mixture by us ofaqueous solvent.

FIG. 11. Schematic flowchart for the separation of long chain amino acidand dibasic acid from a mixture of an alkali hydroxide hydrolysis in anaqueous solvent.

FIG. 12. Schematic flowchart for the separation of inorganic alkali saltand the recovery of the alkali salts of long chain amino acids anddodecanedioic acid from waste aqueous stream.

DESCRIPTION OF THE INVENTION

Hydrolysis of the mixed amide derivatives of the following structures:

from the Beckmann rearrangement of oxime fatty acid derivatives can becarried out with either an acid or a base to yield a mixture of mainproducts of the following structures:

wherein m is an integral from 0 to 10, n is an integral from 6 to 20; Xis OR or NR₁R₂, wherein OR is OH, C₁-C₈ monohydric alcohol or C₁-C₈polyhydric alcohol, and R₁ and R₂ are each independently hydrogen orC₁-C₈ alkyl group.

When m=5, n=10, the main products are 11-aminoundecanoic acid,dodecanedioic acid, hexylamine, and heptanoic acid. Because the startingmaterial of commercial grade is obtained from castor oil, significantamount of stearic acid is also present as an impurity in the mixture ofproducts.

When m=7, n=8, the main products are 9-aminononanoic acid, sebacic acid,octylamine, and pelargonic acid.

When m=5, n=12, the main products are 13-aminotridecanoic acid,tetradecanedioic acid (brassylic acid), hexylamine, and heptanoic acid.

When the hydrolysis reaction of mixed amide derivatives from theBeckmann rearrangement is performed in the presence of alkali hydroxide,main products other than alkylamine are obtained in the form of theiralkali salts. It was observed that a starting suspension of the mixedamide derivatives in a solution of alkali hydroxide is changed to aclear solution at a temperature of 60° C. or above after the hydrolysis.Upon cooling, the clear solution becomes a pasty, non-stirrable cake,because alkali salts of long chain amino acids and dibasic acids arenearly insoluble in an alkali solution as shown in FIG. 6.

The alkali metals are lithium, sodium, potassium, or cesium.

The process according to the present invention, illustrated in FIG. 1for the separation of each component in a mixture of the hydrolysisreaction by the method of alkali hydroxide, starts with removal oflow-boiling components and alkylamine.

The low boiling component comes from alcohols, i.e., methanol orethanol, commonly used in the starting material of keto fatty acidesters. If the mixed amide derivatives are carboxylic acid, little or nolow boiling component is present in the mixture.

These low boiling alcohols, formed by the hydrolysis of esters, aredistilled off from the reaction mixture. Distillation of these lowboiling alcohols can be carried out under normal pressure, increasedpressure, or reduced pressure, during or after the hydrolysis reaction.

Some alkylamines, in particular, of C₁ to C₅, are of lower boilingpoint, and they are distilled off along with alcohols. These alkylaminescan be separated from alcohols according to methods known in prior art.

For the production of 11-aminoundecanoic acid and dodecanedioic acid,hexylamine is one of the main products. Hexylamine is found to form anazeotrope with water and can be separated from the solution byazeotropic distillation. Upon cooling, the distillate separates into anupper phase of nearly pure hexylamine and an aqueous phase containingnot more than 2% of hexylamine. Hexylamine can also be separated fromthe mixture by steam distillation or steam stripping. Completeseparation is accomplished when the distillate at the overhead becomesnearly neutral at a pH of 7-8.

The hexylamine distillate contains a small percentage of water and canbe dried with a drying agent, and preferably, by azeotropic distillationof a small amount of hexylamine to remove the water in hexylamine.

Hexylamine and alkylamines of more than C₇ can also be separated fromthe hydrolysis solution by extraction with an extractant solvent. Thesealkylamines show excellent partition properties between an organicextractant phase and the strongly alkaline aqueous mixture of thehydrolysis reaction. Suitable extractant solvents are selected from theclasses of ester, aliphatics, aromatics, ethers, ketones, andwater-insoluble amines. Preferably, selected extractant solvent is thesame as the solvent chosen for the next stage of the process accordingto the present invention.

Long chain amino acids and dibasic acids exhibit similarly lowsolubility through a wide range of pH from 2 to 10 at room temperature.Their separation from each other necessitates a high dilution with greatdifficulty even when their mixture is not contaminated by otherimpurities of similar properties, such as fatty acids. When thecommercial starting materials, which invariably contain many other fattyacids, are used in the process according to previous disclosure, theproducts, long chain amino acids and dibasic acids, are alwayscontaminated with these fatty acids.

The present inventor carried out extensive studies to overcome theinherent problems imposed by their little difference in solubility forlong chain amino acids and dibasic acids and found in the presentinvention that the solubility of long chain amino acids can be greatlyincreased by reacting these amino acids with an acid to form an acidsalt at increased temperature. At the same time, alkali salts of longchain dibasic acids and fatty acids in the solution are turned intotheir free carboxylic acids, which can be dissolved in an organicsolvent. Complete separation of these long chain amino acids from longchain dibasic acids and fatty acids is thus accomplished by forming anaqueous solution of an acidic salt of these long chain amino acids andan organic extractant phase rich in long chain dibasic acids, shortchain alkanoic acids, and fatty acids.

Suitable acids are an acid of a pKa<5.0. These acids are, but notlimited to, inorganic acids, i.e., hydrochloric acid, hydrobromic acid,hydroiodic acid, sulfuric acid, nitric acid, phosphoric acid; alkyl andaryl sulfonic acids, i.e., methanesulfonic acid, ethanesulfonic acid,propanesulfonic acid, isethionic acid, benzenesulfonic acid,toluenesulfonic acid, xylenesulfonic acid, and sulfamic acid; organiccarboxylic acids: malic acid, maleic acid, tartaric acid, glycolic acid,lactic acid, citric acid, oxalic acid, formic acid, acetic acid, andpropionic acid. One or a mixture of two or more of these acids can beused to form an acidic salt of long chain amino acids.

Preferably, the acid is selected from one of the inorganic acids, andmost preferably, sulfuric acid.

The aim of acidification is to completely convert alkali salts of longchain dibasic acids, short chain alkanoic acids, and fatty acids intofree carboxylic acids and to form an acid salt of long chain amino acid,so as to ensure complete dissolution of long chain amino acid in aqueousphase and long chain dibasic acid in an organic extractant phase.

Organic solvents suitable for extracting dibasic acids and fatty acidsare water-insoluble and belong to the classes of ester, aliphatics,aromatics, ethers, alcohols of C₄ to C₁₀ and ketones of C₄ to C₁₀.Useful solvents include, but not limited to, butyl formate, isobutylformate, butyl acetate, isobutyl acetate, propyl acetate, isopropylacetate, ethyl acetate, ethyl propionate, octyl acetate, benzene,toluene, xylene, cumene, anisole, diethyl ether, diisopropyl ether,dibutyl ether, methyl tert-butyl ether, ethyl tert-butyl ether, methyltetrahydrofuran, petroleum ether, cyclohexane, dichloroethane, methylenechloride, chloroform, carbon tetrachloride, and trifluoromethylbenzene,n-butanol, isobutanol, amyl alcohol, isoamyl alcohol, hexanol,cyclohexanol, 2-ethylhexanol, isooctanol, sec-octanol, butanone,pentanone, hexanone, cyclohexanone, methyl isobutyl ketone. A singlesolvent or a mixture of two or more solvents can be used as extractantsolvent.

Selected extractant solvent is expected to have good solubility of longchain dibasic acid and fatty acid at higher temperature, low or littlesolubility at lower temperature for the long chain dibasic acid and goodsolubility for fatty acid or the like at lower temperature to ensure aneffective separation of long chain dibasic acid from other fatty acidsrich in the organic phase.

Preferably, the extractant solvent is toluene.

The amount of extractant solvent is not limited, but is greater than theeffective amount for the dissolution of dibasic acids and fatty acidimpurities.

Temperature to perform acidification and extraction is in the range from50° C. to the boiling point of the mixture of extractant organic phaserich in long chain dibasic acid and fatty acid and below 100° C. undernormal pressure. Acidification and extraction can also be carried out atelevated temperature under pressure, but pressure equipment will beneeded for the process.

Preferably, acidification and extraction are performed at a temperaturefrom 60° C. to 95° C., and most preferably at a temperature from 80° C.to 90° C. At higher temperature, the higher solubility of long chaindibasic acid in the extractant solvent is advantageous in reducing theamount of the extractant solvent used.

There is no preference as to how an acid and an extractant solvent areintroduced into the solution of alkali salts of long chain amino acidand dibasic acid that have been freed of alkylamine. An acid and anextractant solvent can be added concomitantly, sequentially,continuously, semi-continuously, or batch wise.

When the acidification and extraction are performed according to theprocess of the present invention, good phase separation is achieved. Thepresent inventor unexpectedly found that extractant solvent extractsnearly all colored materials into extractant phase, leaving behind acolorless aqueous solution of the acid salt of long chain amino acid,which provides an added advantage in greatly simplifying thepurification of long chain amino acids.

The present inventor found that a middle phase between the upperextractant phase and lower aqueous phase is formed in some cases andcontains predominantly the acid salt of long chain amino acid and theacid salt of hexylamine, if hexylamine is not removed or removedincompletely from the hydrolysis solution. This middle phase is formed,especially, when the aqueous solution contains a high concentration ofalkali salt. However, the middle phase can be effectively separated andcombined with aqueous phase to recover long chain amino acid.Alternatively, after separating the aqueous phase, the middle phase isdissolved with deionized water at increased temperature.

Although the aqueous solution of the acid salt of long chain amino acidis nearly colorless, to further improve the quality of the isolatedproduct, the solution can be treated with activated carbon to decolorizeand to absorb minor impurities. The treatment can be carried out from50° C. to the boiling point for a period from a few minutes to a fewhours, preferably 30 minutes to 2 hours, most preferably for 1 hour.After filtration, a clear colorless solution is obtained.

In order to isolate long chain amino acid, the strongly acidic aqueoussolution is neutralized with a basic agent to near neutral acidity in apH range from 5 to 9. More preferably, the pH is in the range of 6 to 8.The neutralization is performed at a temperature from 50° C. to theboiling point of the solution, preferably from 60 to 90° C., mostpreferably from 70° C. to 80° C. Neutralization at this most preferredtemperature produces larger crystals that will facilitate solid-liquidseparation. After cooling to 30° C. to 40° C., the product, long chainamino acid, is precipitated and separated by means of solid-liquidseparation, i.e., filtration or centrifuge, to yield a mother liquorcontaining inorganic salt and a small amount of long chain amino acid.

The basic agent is selected from the group consisting of ammonia, alkaliand ammonium salts of hydroxide, bicarbonate, carbonate, sulfite,bisulfite, and carboxylate. A single agent or a mixture of two or moreagents can be used. Preferably, the basic agent is an alkali hydroxide,and most preferably, the same agent used in the hydrolysis reaction ofthe mixed amide derivatives.

The most preferable basic agent is sodium hydroxide.

Treatment of the mother liquor after the isolation of long chain aminoacid is illustrated in FIG. 3 and FIG. 4 to achieve a completeseparation of inorganic salt and full recovery of long chain amino acidwith the aid of an alkali hydroxide or an acid, respectively.

Since long chain amino acid, e.g., 11-aminoundecanoic acid, hasrelatively constant solubility, evaporative concentration of the motherliquor will result in the crystallization of inorganic salt, inparticular, sodium sulfate, along with valuable long chain amino acid.To overcome this difficulty, the present inventor found that thesolubility of 11-aminoundecanoic acid can be drastically increased byincreasing or lowering the pH at increased temperature as illustrated inFIG. 6. In fact, alkali salt of 11-aminoundecanoic acid becomes freelysoluble in 2 M solution of sodium hydroxide at about 50° C. This findinggreatly facilitates the separation of inorganic salt, most preferably,sodium sulfate, and the recovery of long chain amino acids.

Although the solubility of long chain amino acid can be increased byboth an acid and an alkali hydroxide, it is preferable to use an alkalihydroxide, because alkali salt is non-corrosive to commonly used processequipments made of stainless steel.

After adjusting pH of the aqueous stream with an alkali hydroxide, themother liquor is concentrated to crystallize inorganic salt, mostpreferably, sodium sulfate, at a temperature from 40° C. to the boilingpoint of the solution. Evaporative crystallization can be carried outunder normal, reduced, or increased pressure, continuously or in batch.The crystallized salt is removed from the saturated solution by means ofsolid-liquid separation, e.g., filtration or centrifuge.

The basic mother liquor after removal of alkali salt is neutralized withan acid to a neutral pH. The dissolved long chain amino acidprecipitates and can be recovered by means of solid-liquid separation,and the mother liquor is recycled.

The acid used in this step can be selected from the class of inorganicacids, organic carboxylic acids, organic sulfonic acids, sulfamic acid.Preferably, one of the inorganic acids is selected. More preferably, thesame acid is used as in previous step. Most preferably, the acid issulfuric acid.

The extractant phase rich in long chain dibasic acid, short chainalkanoic acid, and fatty acid after the separation of aqueous phase iscooled to a lower temperature in the range of 0° C. to 50° C., morepreferably 0° C. to 30° C., most preferably 10° C. to 20° C. tocrystallize long chain dibasic acid, which can be separated by means ofsolid-liquid separation. Although the extractant phase and filtrationmother liquor is dark in color, the product is nearly white in color andfree of any other fatty acids, such as stearic acid.

The mother liquor is distilled to recover extractant solvent and theresidual is distilled under vacuum to recover short chain alkanoic acid,e.g., heptanoic acid, in nearly pure form.

In one embodiment of the present invention, the extractant phase isfirst concentrated by distillation, then cooled to crystallize longchain dibasic acid in an increased yield.

In another embodiment of the present invention, the extractant phase isfirst distilled to recover extractant solvent, then distilled undervacuum to recover short chain alkanoic acid. To the distillationresidual is added an organic solvent to dissolve the residual byheating, then to crystallize long chain dibasic acid by cooling. Thesolvent is most preferably the original extractant solvent, so that nomixture of different solvents will result to simplify the overallprocess.

In a further embodiment of the present invention, the extractant phaseis distilled to recover solvent and the residual is added to a loweralcohol, in particular methanol or ethanol, most preferably, methanol,in the presence of an esterification catalyst to yield a mixture ofmethyl esters of alkanoic acid, long chain dibasic acid, and other fattyacid originating from starting materials. These methyl esters are thenfractionally distilled to obtain each component in pure form and arefreed of any colored materials. These pure methyl esters are marketeddirectly or can be hydrolyzed to their respective carboxylic acidaccording to process known in prior art.

Alternatively, the mixture of methyl esters is distilled to a mixturethat is freed of any colored materials. The distilled mixture of methylesters are then hydrolyzed to a mixture of alkanoic acid, long chaindibasic acid, and fatty acid, which can be separated according to theprocess of the present invention.

In the case of producing 11-aminoundecanoic acid and dodecanedioic acidaccording to the process of the present invention, the distillationresidual is black in color and contains stearic acid from the startingmaterial of castor oil and a small amount of dodecanedioic acid. Thisdark residual is reacted with a lower alcohol, most preferably,methanol, in the presence of an acid catalyst to form methyl esters. Themixed methyl esters are fractionally distilled to yield colorless methylesters of stearic acid and dodecanedioic acid. The recovered methylstearate is either hydrolyzed to stearic acid or marketed as acommercial product, while the methyl ester of dodecanedioic acid ishydrolyzed to obtain dodecanedioic acid.

When the hydrolysis reaction of mixed amide derivatives from theBeckmann rearrangement is performed with an acid, most preferably,sulfuric acid, alkyl amine and long chain amino acid are obtained in theform of their acid salts, while long chain dibasic acid and fatty acidexist in the form of free carboxylic acid.

After the hydrolysis reaction proceeds to completion, water and anextractant solvent are introduced into the suspension to dissolve theacid salts of long amino acid and alkylamine and to transfer the longchain dibasic acid, short chain alkanoic acid, and other fatty acid intoan extractant phase.

There is no preference as to how water and extractant solvent are addedto the hydrolysis mixture. They can be added concomitantly,sequentially, continuously, semi-continuously, or batch wise. The amountof water added to the reaction mixture is sufficient to effectivelydissolve the acid salts of long chain amino acid and alkylamine. Theextractant solvent is selected on the same principle as described in theprevious section for the extractant solvent for the hydrolysis solutionwith alkali hydroxide.

After dissolution and extraction according to the process of presentinvention, the aqueous phase containing the acid salts of long chainamino acid and alkylamine and the extractant solvent phase rich in longchain dibasic acid and short chain alkanoic acid are separated. An addedadvantage of the present invention is that all colored materials aretransferred into organic extractant phase and the extracted aqueoussolution of long chain amino acid and alkylamine is nearly colorless.

After phase separation, the organic extractant phase is treated in thesame way as for the extractant phase obtained from acidification andextraction of the hydrolysis solution using alkali hydroxide.

The strongly acidic aqueous phase is neutralized with a basic agent to aneutral pH in the range of 5 to 9, more preferably 5 to 8, mostpreferably 6 to 7, to precipitate long chain amino acid. After cooling,the precipitated solid is isolated by means of solid-liquid separation,i.e., filtration or centrifuge.

The basic agent is selected from ammonia, alkali and ammonium salts ofhydroxide, bicarbonate, carbonate, bisulfite, sulfite, and carboxylate.Preferably, the basic agent is alkali hydroxide or ammonium hydroxide,and most preferably, sodium hydroxide.

The mother liquor obtained after the isolation of long chain amino acidcan be treated according to the scheme illustrated in FIG. 5 to separatealkylamine, inorganic salt, and to recover dissolved long chain aminoacid.

When sodium hydroxide is used as the basic agent to neutralize sulfuricacid, more sodium hydroxide is added to the mother liquor to a basic pH,alkylamine can be extracted with an extractant solvent, or preferably byazeotropic distillation. After complete removal of alkylamine, thesolution is further evaporated to separate inorganic salt, preferably,sodium sulfate. Long chain amino acids can be recovered by adding anacid to adjust the pH to neutral.

If ammonia or ammonium hydroxide is used as the basic agent toneutralize sulfuric acid, and after more basic agent is added to themother liquor to a basic pH, alkylamine can only be recovered byextraction. Distillation of the basic solution will remove ammoniainstead of alkylamine.

In an alkali hydroxide hydrolysis of the mixed amide derivatives, twomole equivalents of alkali hydroxide are required, but more than twoequivalents, usually between 2.5 to 3 equivalents of alkali hydroxideare used to achieve a complete hydrolysis. The excess basic agentconsumes additional acid and generate an extra amount of inorganic salt.The present inventor found that alkali salts of long chain amino acidand dibasic acid have little solubility at room temperature in water orin a solution of alkali hydroxide, as illustrated in FIG. 6 and FIG. 7,and can be crystallized from the hydrolysis solution. Upon cooling, amixture of alkali salts of long chain dibasic acid and amino acid isprecipitated. After separation of these insoluble salts, the excessalkali hydroxide can be recycled to the hydrolysis stage to reduce theuse of alkali hydroxide. The recycling can be performed until theconcentration of alkali salt of alkanoic acid becomes saturated, atwhich point, the mother liquor is purged from the hydrolysis stage andacidified with an acid to form alkanoic acid.

Precipitation of the alkali salts of long chain amino acid and dibasicacid can be carried out at temperature from 0° C. to 40° C., preferablyfrom 10° C. to 30° C., most preferably from 15° C. to 25° C. At thispreferable temperature, alkali salts are precipitated in high yield.

Alternatively, the hydrolysis solution is cooled to precipitate alkalisalts of long chain dibasic acid and amino acid, which are separated bymeans of a solid-liquid separation to provide a mother liquor.Alkylamine is then recovered from the mother liquor by distillation orextraction with an extractant solvent.

Precipitation of the alkali salts of long chain amino acid and dibasicacid is performed preferably after removal of alkylamine, but theprecipitation can also be carried out before removing alkylamine, infact, little difference is observed if alkylamine is not removed first.

Preferably, alkylamine is removed from the solution beforeprecipitation, because the strongly alkaline hydrolysis solution makesalkylamine removal from the solution convenient to perform bydistillation or by extraction with an extractant solvent.

Acidification of the mother liquor with an acid results in the formationof alkanoic acid. The alkanoic acid can be separated by phaseseparation, or it can be extracted with an extractant solvent. Alkanoicacid of required purity can be obtained by distillation.

The mixed alkali salts of long chain amino acid and dibasic acid can beused directly for the separation or they can first be converted to amixture of long chain amino acid and dibasic acid before the separation.To prepare a mixture of long chain dibasic acid and amino acid, theiralkali salts are dissolved or suspended in water and neutralized with anacid to a pH in the range from 4 to 5. The alkali salts are converted toa mixture of their respective long chain dibasic acid and amino acid.

A mixture of long chain amino acid and dibasic acid can be separated byselectively dissolving long chain dibasic acid in an aqueous solution ofammonia, ammonium hydroxide, ammonium bicarbonate, ammonium carbonate,alkylamines, or a mixture of two or more thereof. Upon removal of excessammonia or alkylamine by heating, long chain dibasic acid is convertedto the ammonium salt, which is soluble in water, while the amino acid isnearly insoluble. The long chain amino acid is recovered by means ofsolid-liquid filtration, while the long chain dibasic acid, dissolved inthe mother liquor as the ammonium salt, is recovered by adding an acidto convert the ammonium salt to long chain dibasic acid.

The mixture of long chain amino acid and dibasic acid or their alkalisalts can be separated into long chain amino acid and dibasic acid byfirst dissolving or suspending in water, adding an acid in the presenceof an extractant solvent to form an aqueous solution of an acid salt oflong chain amino acid and an extractant solvent phase containing longchain dibasic acid according to process disclosed in the presentinvention.

Although the alkali salts are nearly insoluble in water and organicsolvents, the present inventor found that the solubility of the alkalisalts of long chain amino acid and dibasic acid can be drasticallyaltered by using an aqueous solvent. For example, FIG. 8 illustrates thesolubility change of sodium salts of 11-aminoundecanoic acid anddodecanedioic acid in aqueous ethanol. Sodium salts of11-aminoundecanoic acid and dodecanedioic acid are nearly insoluble inboth water and ethanol, but aqueous ethanol drastically increases thesolubility of sodium of 11-aminoundecanoic acid, while the sodium saltof dodecanedioic acid remains unchanged. This surprising finding rendersthe separation of these two salts possible.

Suitable solvents include, but not limited to, methanol, ethanol,propanol, isopropanol, tert-butanol, n-butanol, isobutanol, sec-butanol,ethylene glycol, propylene glycol, diethylene glycol, glycerol,tetrahydrofuran, dioxane, morphine, N-methyl morphine, dimethylformamide, dimethyl acetamide, N-methylpyrrolidone, tetramethylurea, anda mixture of two or more thereof. Preferable solvent is selected fromone of the lower alcohols.

The most preferable solvent is ethanol.

The concentration of aqueous ethanol is from 20% to 90%, preferably from40% to 80%, most preferably from 50% to 70%.

In order to separate the alkali salts of long chain amino acid anddibasic acid, the mixed salts can be stirred in an aqueous solution ofselected solvent at a temperature from 0° C. to 40° C., preferably from15° C. to 25° C. from 30 minutes to 2 hours. Alkali salt of long chainamino acid dissolves while alkali salt of long chain dibasic acidremains as solid. More preferably, the mixed salts are heated in anaqueous solvent to dissolve, then cooled to crystallize the alkali saltof long chain dibasic acid.

The amount of an aqueous solvent is greater than the effective amount todissolve alkali salt of long chain amino acid. Too large an amount is tobe avoided as a small amount of alkali salt of long chain dibasic acidwill dissolve and complicate the separation.

The insoluble alkali salt of long chain dibasic acid in an aqueoussolvent is separated by means of solid-liquid separation from solublealkali salt of long chain amino acid. Long chain dibasic acid isrecovered by adding an acid to an aqueous suspension or solution of thealkali salt, then by means of solid-liquid separation.

The mother liquor after the separation of alkali salt of long chaindibasic acid is distilled to recover solvent and the aqueous solution ofalkali salt of long chain amino acid is neutralized with an acid to a pHin the range from 5 to 9 to recover the long chain amino acid.

FIG. 11 demonstrates an integrated process for an alkali hydroxidehydrolysis of the mixed amide derivatives in an aqueous solvent, mostpreferably, ethanol, for a direct isolation of the alkali salt of longchain dibasic acid and the alkali salt of long chain amino acid withoutisolating their mixture.

After the hydrolysis is completed, the solution is cooled to crystallizethe alkali salt of long chain dibasic acid. The crystallization takesplace at a temperature in the range from 0° C. to 40° C., morepreferably from 15° C. to 25° C. The crystallized salt of long chaindibasic acid is separated by means of solid-liquid separation, i.e.,filtration or centrifuge, to provide a mother liquor.

The mother liquor is distilled first to recover solvent and then toremove alkylamine. The residual solution of distillation is then cooledto crystallize the alkali salt of long chain amino acid, which isseparated by means of solid-liquid separation, i.e., filtration orcentrifuge, to provide a mother liquor containing mainly alkali salt ofalkanoic acid. The crystallization of the alkali salt of long chainamino acid takes place at a temperature in the range from 0° C. to 40°C., more preferably from 15° C. to 25° C.

The alkali salt of long chain dibasic acid and amino acid can be furtherpurified by recrystallization in water or an aqueous solvent.

Long chain dibasic acid is obtained by dissolving or suspending thealkali salt in water, acidified to a pH in the range from 1 to 5, morepreferably from 3-4, with an acid. After completion of crystallization,the crystalline solid is separated by means of solid-liquid separation.

Long chain amino acid is obtained by dissolving or suspending the alkalisalt in water, which is then neutralized with an acid to a pH in therange from 5 to 9, more preferably in the range from 6 to 8.

The mother liquor containing the alkali salt of alkanoic acid alsocontains excess alkali hydroxide. This solution can be recycled to thehydrolysis stage to make use of the excess alkali hydroxide until theconcentration of alkali salt of short chain alkanoic acid becomessaturated. The solution is then purged from the process and acidifiedwith an acid to yield alkanoic acid, which can be isolated by a phaseseparation or by extraction with an extractant solvent.

The aqueous stream, generated as waste water after the separation oflong chain amino acid, dibasic acid, or alkanoic acid, containsinorganic salt, most preferably sodium sulfate, if sulfuric acid andsodium hydroxide are selected as the most preferable acid and basicagent respectively, is treated according a scheme illustrated in FIG. 12to isolate alkali salt and to recover alkali salts of long chain aminoacid and dibasic acid. An alkali hydroxide is introduced to an aqueousstream to increase the solubility of alkali salts of long chain aminoacid and dibasic acid at higher temperature so as to facilitate theisolation of alkali salt by evaporative crystallization. The motherliquor is then cooled to precipitate a mixture of alkali salts of longchain dibasic acid and amino acid, which is separated by means ofsolid-liquid separation. The mother liquor is returned to the beginningstep to complete a cycle. This cyclic process ensures that no waste,other than inorganic salt, will be discharged from the process.

The process according to the present invention achieves a completeseparation of each component in the production of long chain amino acidsand dibasic acids without discharging any waste aqueous stream from theprocess.

EXAMPLES

The following examples illustrate the practice of this invention but arenot intended to limit its scope.

Example 1

This example relates to the separation of 11-aminoundecanoic acid,dodecanedioic acid, hexylamine, heptanoic acid, and stearic acid fromtheir mixture obtained from sodium hydroxide hydrolysis of the mixedamide derivatives.

A mixture of the starting solution was obtained by hydrolyzing 150 g ofthe mixed amide derivatives prepared from methyl 12-ketostearateaccording to WO2017/088218 with 60 g of sodium hydroxide in 800 mL ofwater.

The solution was azeotropically distilled with a 2.5×30 cm vacuumjacketed column packed with porcelain berl saddles, first to obtainmethanol, then an azeotrope of hexylamine-water until the pH of theoverhead became neutral at a pH of 7-8. The distillate was separatedinto two phases and the lower aqueous phase was continuously returned tothe distillation flask. The crude hexylamine was dehydrated byazeotropic distillation to yield 20.5 g of hexylamine.

To the residual solution were added 800 mL of toluene, followed by 100 gof sulfuric acid. The mixture was vigorously stirred for 60 minutes at85° C. and transferred to a separatory funnel to separate the aqueousphase. The dark-colored upper toluene phase was washed with hotdeionized water and the washing was combined with the aqueous phase.

To the colorless aqueous phase was added 1.0 g of activated carbon andstirred at 80° C. for 45 minutes and the solution was filtrated toobtain a clear, colorless solution. The solution was neutralized with asolution of sodium hydroxide to a pH of 7.5 at about 70° C. to yield acrystalline suspension. After cooling to 35° C., the suspension wasfiltrated and the solid material washed three times with deionizedwater. After drying, 42.5 g of white 11-aminoundecanoic acid wasobtained.

To the mother liquor of about 1200 mL was added 1.0 g of sodiumhydroxide. The solution was concentrated and sodium sulfate removed byfiltration three times so that 300 mL of solution remained. This basicsolution was adjusted with dilute sulfuric acid to a pH of 7.5 torecover another 0.8 g of 11-aminoundecanoic acid.

The toluene solution was washed with hot deionized water once and cooledon ice to 5° C. to obtain a crystalline suspension. After filtration,washing with cold toluene, and drying, 45.2 g of dodecanedioic acid wasobtained. The product was off-white.

The toluene filtrate was combined with toluene washing and distilled torecover toluene. The residual was then vacuum distilled with a shortpath column to yield 24.5 g of heptanoic acid.

The residual after distillation was black and weighted 26.6 g. Theresidual was mixed with 200 mL of methanol and added 1.0 g of sulfuricacid. After the mixture was refluxed for 2 hours and sulfuric acid wasneutralized with sodium methoxide. Methanol was removed by distillationand the residual methyl esters were distilled to obtain a mixture ofcolorless methyl esters, of which 80% was methyl stearate, 5% was methylheptanoate, 15% was dimethyl dodecanedioate. About 1.5 g of blackresidual remained in the distillation flask.

Example 2

This example relates to the separation of 11-aminoundecanoic acid,dodecanedioic Acid, hexylamine, heptanoic acid, and stearic acid fromtheir mixture of sulfuric acid hydrolysis of the mixed amidederivatives.

A mixture of the starting suspension was obtained by hydrolyzing 150 gof the mixed amide derivatives prepared from methyl 12-ketostearateaccording to WO2017/088218 with a mixture of 150 g of sulfuric acid and30 g of water. During the hydrolysis, low-boiling methanol wascontinuously removed.

To the reaction suspension were added 800 g of water and 800 mL oftoluene. The mixture was vigorously stirred for 60 minutes at 85° C. andtransferred to a separatory funnel to separate the two phases.

The toluene phase was treated the same way as in Example 1 and similarresults were obtained for each component.

The aqueous phase was neutralized with aqueous solution of sodiumhydroxide to neutral pH at 7.5 for a total of 115 g of sodium hydroxide.After cooling to 35° C., the crystalline solid was filtered off, washedthree times with deionized water, dried to yield 41.6 g of11-aminoundecanoic acid.

To the mother liquor was added an additional solution of sodiumhydroxide containing 20 g of sodium hydroxide. The solution wasazeotropically distilled with a 2.5×30 cm vacuum jacketed column filledwith porcelain berl saddles until the pH of the overhead became a pH of7-8. The distillate is separated into two phases and the lower aqueousphase was continuously returned to the distillation flask. The crudehexylamine was dehydrated by azeotropic distillation to yield 21.5 g ofhexylamine.

After hexylamine was completely removed, the solution containing sodiumsulfate was treated the same way as in Example 1. An additional 1.2 g of11-aminoundecanoic acid was recovered from the mother liquor.

Example 3

This example relates to the separation of 9-aminononanoic acid, sebacicacid, octylamine, and pelargonic acid.

A mixture of the starting solution was obtained by hydrolyzing 150 g ofthe mixed amide derivatives prepared from methyl 10-ketostearateaccording to WO2017/088218 with 60 g of sodium hydroxide in 800 mL ofwater.

To the turbid solution was added 200 mL of toluene and the mixture wasvigorously stirred at a temperature of 80° C. for 45 minutes.Afterwards, the toluene phase was separated and removed to yield aresidual, which was distilled to obtain 29.5 g of n-octylamine.

The aqueous phase was treated the same way as in Example 1 to obtain36.9 g of pelargonic acid, 39.6 g of 9-aminononanoic acid, and 45.5 g ofsebacic acid.

Example 4

This example relates to the separation of 13-aminotridecanoic acid,brassylic acid, hexylamine, and heptanoic acid.

A mixture of the starting solution was obtained by hydrolyzing 180 g ofthe mixed amide derivatives prepared from methyl ester of14-ketoarachidic acid according to WO2017/088218 with 60 g of sodiumhydroxide in 800 mL of water.

The reaction solution was treated the same way as in Example 1 to yield23.5 g of hexylamine, 29.4 g of heptanoic acid, 53.1 g of13-aminotridecanoic acid, and 62.9 g of brassylic acid.

Example 5

This example relates to the separation of 11-aminoundecanoic acid,dodecanedioic acid, hexylamine, heptanoic acid, and stearic acid by themethod of co-precipitation of sodium salts of 11-aminoundecanoic acidand dodecanedioic acid.

A mixture of the starting solution was obtained by hydrolyzing 150 g ofthe mixed amide derivatives prepared from methyl 12-ketostearateaccording to WO2017/088218 with 60 g of sodium hydroxide in 800 mL ofwater.

The solution was azeotropically distilled with a 2.5×30 cm vacuumjacketed column packed with porcelain berl saddles, first to obtainmethanol, then an azeotrope of hexylamine-water until the pH of theoverhead became neutral at a pH of 7-8. The distillate was separatedinto two phases and the lower aqueous phase was continuously returned tothe distillation flask. The crude hexylamine was dehydrated byazeotropic distillation to yield 20.5 g of hexylamine.

To the residual solution of distillation was added 500 mL of water. Thesolution was slowly stirred while cooling to room temperature. Theprecipitate was then filtered and washed with cold water to give amixture of the alkali salts of 11-aminoundecanoic acid and dodecanedioicacid. Half of the mother liquor is recycled to the hydrolysis stage. Theother half is concentrated to 300 mL and acidified with sulfuric acid toyield an oily layer of heptanoic acid.

The solid material was dissolved in 500 mL of 65% aqueous ethanol byheating and then slowed cooled to room temperature to crystallize sodiumsalt of dodecanedioic acid. After filtration and washing with water, themother liquor is distilled to recover ethanol and the aqueous solutionwas neutralized with sulfuric acid to a pH of 6-7 to yield 41.4 g of11-aminoundecanoic acid.

The sodium salt of dodecanedioic acid was suspended in 400 mL of waterand acidified with sulfuric acid to yield 46.3 g of dodecanedioic acid.

Example 6

This example relates to the sodium hydroxide hydrolysis of the mixedamide derivatives in aqueous ethanol and the separation of11-aminoundecanoic acid, dodecanedioic acid, hexylamine, and heptanoicacid.

A mixture of the starting solution was obtained by hydrolyzing 160 g ofthe mixed amide ethyl ester prepared from ethyl 10-ketostearateaccording to WO2017/088218 with 60 g of sodium hydroxide in 800 mL of65% aqueous ethanol.

The solution after hydrolysis was cooled slowly to room temperature andthe crystallized sodium salt of dodecanedioic acid was filtered andwashed with dilute aqueous ethanol. The solid material was suspended in300 mL of water, to which was added sufficient sulfuric acid to a pH of2. The solid material was filtered and washed three times with deionizedwater to give 46.8 g of dodecanedioic acid.

The alcoholic mother liquor was distilled with a 2.5×30 cm vacuumjacketed column packed with porcelain berl saddles, first to obtainethanol, then an azeotrope of hexylamine-water until the pH of theoverhead became neutral at a pH of 7-8. The distillate was separatedinto two phases and the lower aqueous phase was continuously returned tothe distillation flask. The crude hexylamine was dehydrated byazeotropic distillation to yield 21.4 g of hexylamine.

To the residual solution of ethanol distillation was added 400 mL ofwater. The solution was slowly stirred while being cooled to roomtemperature to crystallize sodium salt of 11-aminoundecanoic acid. Afterfiltration and washing with water, the solid was suspended in 200 mL ofwater and neutralized with sulfuric acid to a pH of 7.5. Filtration,washing with deionized water, and drying, yield 40.9 g of11-aminoundecanoic acid.

The mother liquor after separating the sodium salt of 11-aminoundecanoicacid was concentrated to a volume of 300 mL, and acidified with sulfuricacid to give an oily upper layer of heptanoic acid, which was separatedby phase separation.

The aqueous streams were combined and added 2 g of sodium hydroxide. Thesolution were boiling to crystallize sodium sulfate, which was filteredat 80° C. and washed with hot saturated solution of sodium sulfate. Themother is then cooled slowly to 35° C. to crystallize sodium salt of11-aminoundecanoic acid and dodecanedioic acid, which was recovered byfiltration.

It will be understood that the foregoing examples, explanation, anddrawings are for illustrative purpose only and that in view of theinstant disclosure various modifications of the present invention willbe self-evident to those skilled in the art and are to be includedwithin the spirit and purview of this application and the scope of theclaims.

What is claimed is:
 1. A process for the separation from an aqueousstream of long chain amino acid, dibasic acid, short chain alkylamine,and alkanoic acid of the following structures:

from at least two of them in an alkali hydroxide hydrolysis mixture ofthe mixed amide derivatives of the following structures:

wherein m is an integer from 0 to 10; n is an integer from 6 to 20; X isOR or NR₁R₂, wherein OR is OH, C₁-C₈ monohydric alcohol, or C₁-C₈polyhydric alcohol, and R₁ and R₂ are each independently hydrogen orC₁-C₈ alkyl group; comprising: (1) cooling the alkali hydroxidehydrolysis solution of mixed amides to precipitate a mixture of alkalisalts of long chain amino acid and dibasic acid; (2) separating themixture of alkali salts of long chain amino acid and dibasic acid bymeans of solid-liquid separation to provide a mother liquor comprisingalkali salt of alkanoic acid; and (3) separating long chain amino acidand dibasic acid from their mixture or a mixture of their alkali saltsby acidification-extraction of long chain dibasic acid with anextractant solvent and an acid, or by selective dissolution of thealkali salt of long chain amino acid in an aqueous solvent, or byselective dissolution of long chain dibasic acid in an aqueous solutionof ammonium hydroxide, or ammonium bicarbonate, or ammonium carbonate ortheir mixture.
 2. The process according to claim 1, wherein mixed alkalisalts of long chain amino acid and dibasic acid are precipitated at atemperature from 0° C. to 40° C.
 3. The process according to claim 1,wherein mixed alkali salts of long chain amino acid and dibasic acid areprecipitated at a temperature from 15° C. to 25° C.
 4. The processaccording to claim 1, wherein an aqueous solvent for separating alkalisalts of long chain amino acid and dibasic acid is selected from thegroup consisting of an aqueous solution of methanol, ethanol, propanol,isopropanol, tert-butanol, n-butanol, isobutanol, sec-butanol, ethyleneglycol, propylene glycol, diethylene glycol, glycerol, tetrahydrofuran,dioxane, morphine, N-methylmorphine, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, tetramethylurea, and a mixture of two ormore thereof.
 5. The process according to claim 1, wherein the aqueoussolvent is aqueous ethanol.
 6. The process according to claim 5, whereinthe aqueous ethanol contains from 20% to 90% of ethanol.
 7. The processaccording to claim 5, wherein the aqueous ethanol contains from 40% to70% of ethanol.
 8. The process according to claim 1, wherein a processfor preparing a mixture of long chain dibasic acid and amino acid fromtheir alkali salts in step (3) comprises: (a) adding an acid to anaqueous solution or suspension of the alkali salts of long chain dibasicacid and amino acid to a pH in the range from 4 to 5; and (b) separatingthe mixture of long chain dibasic acid and amino acid by means ofsolid-liquid separation.
 9. The process according to claim 1, wherein aprocess for separating long chain amino acid and dibasic acid from theirmixture in step (3) comprises: (a) suspending the mixture of long chainamino and dibasic acid in an aqueous solution of ammonia or ammoniumhydroxide, or ammonium bicarbonate, or ammonium carbonate, or theirmixture to dissolve long chain dibasic acid; (b) separating long chainamino acid by means of solid-liquid separation to provide a motherliquor; and (c) adding an acid to the mother liquor of step (b) toprecipitate long chain dibasic acid.
 10. The process according to claim1, wherein a process for separating long chain amino acid and dibasicacid in step (3) comprises: (a) adding an acid to an aqueous suspensionor solution of a mixture of long chain amino acid and dibasic acid or amixture of the alkali salts of long chain amino acid and dibasic acid inthe presence of an extractant solvent; (b) separating the mixture ofstep (a) into an aqueous phase containing the acid salt of long chainamino acid and an extractant phase containing long chain dibasic acid;(c) neutralizing the aqueous phase of step (b) with a basic agent toyield long chain amino acid; (d) cooling the extractant phase tocrystallize the long chain dibasic acid; and (e) separating the longchain dibasic acid by means of solid-liquid separation.
 11. The processaccording to claim 1, wherein a process for separating long chain aminoacid and dibasic acid in step (3) comprises: (a) suspending ordissolving mixed alkali salts of long chain amino acid and dibasic acidin an aqueous solvent; (b) cooling to crystallize the alkali salt oflong chain dibasic acid; (c) separating the precipitate by means ofsolid-liquid separation to provide a mother liquor; (d) adding an acidto an aqueous suspension or solution of the precipitate of step (c) toacidic pH to yield long chain dibasic acid; and (e) distilling themother liquor of step (c) to recover solvent and adding an acid toneutralize the solution to yield long chain amino acid.
 12. The processaccording to claim 1, wherein a process for treating the aqueous streamto recover inorganic alkali salt and a mixture of alkali salts of longchain dibasic acid and amino acid comprises: (a) adding an alkalihydroxide to the aqueous stream to increase the solubility of long chaindibasic acid and amino acid; (b) concentrating the solution of step (a)to crystallize the inorganic alkali salt and to remove the solid byliquid-solid separation to provide a mother liquor; (c) cooling themother liquor of step (b) to precipitate a mixture of alkali salts oflong chain dibasic acid and amino acid; and (d) separating the mixtureof alkali salts of long chain dibasic acid and amino acid bysolid-liquid separation.
 13. The process according to claim 1, whereinthe acid is selected from the group consisting of hydrochloric acid,hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid,phosphoric acid, methanesulfonic acid, ethanesulfonic acid,propanesulfonic acid, isethionic acid, benzenesulfonic acid,toluenesulfonic acid, xylenesulfonic acid, sulfamic acid, malic acid,maleic acid, tartaric acid, glycolic acid, lactic acid, citric acid,oxalic acid, formic acid, acetic acid, propionic acid, and a mixture oftwo or more thereof.
 14. The process according to claim 1, wherein theextractant solvent is selected from the group consisting of butylformate, isobutyl formate, butyl acetate, isobutyl acetate, propylacetate, isopropyl acetate, ethyl acetate, ethyl propionate, octylacetate, benzene, toluene, xylene, cumene, anisole, diethyl ether,diisopropyl ether, dibutyl ether, methyl tert-butyl ether, ethyltert-butyl ether, methyl tetrahydrofuran, petroleum ether, cyclohexane,dichloroethane, methylene chloride, chloroform, carbon tetrachloride,trifluoromethylbenzene, n-butanol, isobutanol, amyl alcohol, isoamylalcohol, hexanol, cyclohexanol, 2-ethylhexanol, isooctanol, sec-octanol,butanone, pentanone, hexanone, cyclohexanone, methyl isobutyl ketone,and a mixture of two or more thereof.
 15. The process according to claim1, wherein the long chain amino acids are 9-aminononanoic acid,11-aminoundecanoic acid, or 13-aminotridecanoic acid.
 16. The processaccording to claim 1, wherein the long chain amino acid is11-aminoundecanoic acid.
 17. The process according to claim 1, whereinthe long chain dibasic acids are sebacic acid, dodecanedioic acid, orbrassylic acid.
 18. The process according to claim 1, wherein the longchain dibasic acid is dodecanedioic acid.
 19. The process according toclaim 1, wherein the short chain alkanoic acid is heptanoic acid. 20.The process according to claim 1, wherein the alkylamine isn-hexylamine.
 21. The process according to claim 1, wherein alkalihydroxides are lithium, sodium, potassium or cesium hydroxide.
 22. Theprocess according to claim 1, wherein alkylamine is recovered from thealkali hydrolysis solution of mixed amides by distillation or byextraction with an extractant solvent.
 23. The process according toclaim 22, wherein the extractant solvent is selected from the groupconsisting of butyl formate, isobutyl formate, butyl acetate, isobutylacetate, propyl acetate, isopropyl acetate, ethyl acetate, ethylpropionate, octyl acetate, benzene, toluene, xylene, cumene, anisole,diethyl ether, diisopropyl ether, dibutyl ether, methyl tert-butylether, ethyl tert-butyl ether, methyl tetrahydrofuran, petroleum ether,cyclohexane, dichloroethane, methylene chloride, chloroform, carbontetrachloride, trifluoromethylbenzene, n-butanol, isobutanol, amylalcohol, isoamyl alcohol, hexanol, cyclohexanol, 2-ethylhexanol,isooctanol, sec-octanol, butanone, pentanone, hexanone, cyclohexanone,methyl isobutyl ketone, and a mixture of two or more thereof.
 24. Theprocess according to claim 1, wherein the mother liquor comprising thealkali salt of alkanoic acid is acidified with an acid to yield alkanoicacid.
 25. The process according to claim 24, wherein the acid isselected from the group consisting of hydrochloric acid, hydrobromicacid, hydroiodic acid, sulfuric acid, nitric acid, phosphoric acid,methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid,isethionic acid, benzenesulfonic acid, toluenesulfonic acid,xylenesulfonic acid, sulfamic acid, malic acid, maleic acid, tartaricacid, glycolic acid, lactic acid, citric acid, oxalic acid, formic acid,acetic acid, propionic acid, and a mixture of two or more thereof.